Clear air turbulence (CAT) occurs at typical jet cruise altitudes, due to a number of different factors, including: the location of the jet stream, the location of the tropopause boundary, the location of localized severe weather including thunderstorms, and the location of mountainous terrain. However, all clear air turbulence phenomena have one thing in common: the phenomena occur in clear air, and aircraft currently have very few ways to avoid these phenomena except to maneuver or change flight altitudes once they have entered the turbulent region.
Turbulence (especially CAT), is a serious concern for air travel. Some airlines take strong measures to avoid regions of forecast or previously discovered turbulence, sometimes flying many extra miles to avoid turbulence. In many areas of the country, the number of options available to an airline to reroute a flight are limited due to airspace capacity or air traffic control system constraints. There are many efforts to improve the identification of turbulent air, however, these efforts only help after one or more flights has flown into rough air, and they don't provide a way to constantly scan the airspace. Currently, there is no affordable, reliable way for an airplane to detect CAT in time to take evasive action.
The problem with CAT is that it occurs in clear air in the absence of particulate matter, such as clouds. Many existing methods of detecting turbulence are dependent upon the existence of particulate matter (moisture, dust, etc.) in the air, which does not help with the detection of CAT in the cruise altitudes at which aircraft (commercial, military, or unmanned air vehicles (UAVs)) can fly. For example, in the high clean air where airliners fly, CAT is often undetectable to Doppler radar or lidar systems that rely on particles in the air.
Previous work has demonstrated that it is technically feasible to detect CAT using scintillation of GPS signals. However, these previous methods were not able to solve the problem of accurately locating the turbulent air with respect to range from the GPS receiver. Prior methods could only determine the existence of turbulence somewhere along the signal's path (along the line of sight to the satellite). Other evaluated methods are too expensive or heavy to be practical for installation aboard an aircraft.
Thus, it is desirable to have a cost effective system and methods for detecting CAT to increase air traffic system capacity by more precisely pinpointing the range and altitude of turbulence before the aircraft penetrates the turbulent air region. It is further desirable for the system and methods to allow air traffic systems and operators to more precisely plan for avoiding these turbulent air regions.
Other desirable features and characteristics of embodiments of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.